<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>css绘制三角形</title>
  <style>
    div {
      margin: 0 auto;
      width: 0;
      height: 0;
      border: 50px solid transparent;
      border-bottom-color: #000;
    }
  </style>
</head>

<body>
  <div></div>
</body>

</html>